With the rapid development of information technology, various hybrid multilayer boards are increasingly being designed and applied to realize high-frequency and high-speed signal transmission and rapid heat dissipation and conduction and to minimize the production cost. As indispensable materials of electronic products, more and more printed circuit boards (PCBs) are needed along with the increasing requirement for consumer electronic products. With the characteristics of flexibility and wire configuration in a three-dimensional space, FPCs are nowadays widely applied to computers, peripheral equipment of the computers, communication products, consumer electronic products, and the like, under the development tendency emphasizing light, thin, small, flexible and high-frequency technological electronic products.
In the high-frequency field, the insertion loss of wireless infrastructure needs to be as low as possible to effectively increase the energy utilization rate. Along with the requirement for 5G communication, millimeter-waves, high-frequency and high-speed accelerator FPCs/PCBs in the aviation and military industry, the rising of emerging industries such as big data and Internet of Things, and the popularization of mobile internet terminals, rapid information processing and transmission have become the focus of the communication industry. In the communication field, further 5G networks will have a higher-speed bandwidth, denser base station construction and a higher network speed than existing 4G networks. To meet the requirement for the Internet of Things, cloud computation and various new-generation broadband communications, high-speed servers and mobile phones with higher transmission speeds have become the development tendency on the market. Generally, FPCs/PCBs are the main bottleneck of the whole transmission process, and the lack of favorable designs and relevant materials with good electrical properties will severely affect the transmission speed or result in signal losses. To overcome the bottleneck, high requirements are put forward for materials of PCBs. Moreover, high-frequency boards mainly used in this industry at present are liquid crystal polymer (LCP) boards and polytetrafluoroethylene (PTFE) fiber boards, but these boards are also limited by the manufacturing process, which has a high requirement for equipment and has to be operated in a high-temperature environment (>280° C.), accordingly, causing a non-uniform film thickness which in turn results in difficult control over the resistance value of the circuit boards. In addition, LCP or PTFE may be squeezed in the high-temperature lamination process, which affects the conductivity of plated copper and causes open circuits, thus, resulting in low confidence and reducing reliability. Moreover, due to the fact that a quick press cannot be used, processing is difficult. Besides, in the high-temperature SMT process or other FPC processes such as the bending process and the strong-acid or strong-alkali liquor preparation process, the yield can be decreased due to poor peel strength. Although other resin films do not have such problems, these resin films have the problems of poor electrical properties or poor mechanical strength.